Pretty sure 750 ml of homemade simple syrup with the appropriate amount of bitters is going to be way less than $14.
Edit: So to be clear, are we talking just the mix part, or a mix that already has whiskey in it. If it includes the booze, then I'm going to assume it's a very base level, 80 proof bourbon. Something I would be unlikely to ever buy for my home bar. I make my house old fashioneds with OF 100 Rye at $26 for a liter bottle. That's $0.77/oz. If I'm pre-mixing a 750 ml bottle of old fashioneds, then I'll use about 22 oz of whiskey. ($17) I make my simple syrup with turbinado sugar and will add about 2.5 oz. ($1-2 or less?) and will add about 25-30 shakes of bitters. Generally a mix of regular and orange Angostura bitters. So maybe another $1-2? Roughly $20 total for about 10 cocktails, and I'll happily put this up against any $14 pre-bottled old fashioned mix.